Fresh water is becoming one of the scarcest natural resources in the world, and it's only going to get worse, said Reno Harnish, director for the Center for Environment and National Security at Scripps Institution of Oceanography. "Because of rising consumption levels due to rising population and declining supplies of clean, potable water."

Population growth and climate change are rapidly draining the global supply of potable water. Scientists and water officials from around the world teamed up in San Diego this week to look for solutions.

More than 2.5 billion people around the world could be without safe drinking water by 2050. That’s why scientists and water officials from around the world gathered this week to discuss the issue at a two-day forum in La Jolla.

In California, reservoirs are full from last year’s abundance of snow and rainfall. But a history of drought, combined with climate change and a growing population, threaten to diminish the region’s fresh water.

“Climate change is going to exacerbate that over the course of the next 50 years," said Harnish. "And so we cannot be complacent. We have to have dialogue about desalination, about purification of water, about conservation of water ... .”

The water shortage also threatens human welfare and the stability of governments, "as people could be forced to migrate or fight for water," he said.

"Look at Singapore, Singapore has made themselves highly independent of water streams from outside of their country by using a lot more purification. They don't want to be dependent on other states," said Harnish. "Another example is Israel, where 80 percent of their water is reused. For them it's a national-security issue of having adequate supplies of water."

Scientists have said global climate change takes on many forms, causing droughts in some areas while increasing flooding and the severity of cyclones in others. Droughts reduce water supply, and floods destroy the quality of water. Rising sea levels could increase the salt content at the mouths of many rivers.

Lake Mead, a key source of water for millions of people in the Southwest, including California, could be dry by 2021 if climate changes and future water usage are not curtailed, according to a 2008 study.

Without Lake Mead and neighboring Lake Powell, the Colorado River system has no buffer to sustain the population.